Sunday, June 06, 2010

Power Line Communications on agenda at ITU

From Southgate Amateur Radio Club, UK:
Power Line Communications on agenda at ITU

ITU Working Parties 1A and 1B will meet in Geneva between June 21 and 28. A major item of discussion will be protection of radio services from interference from Power Line Communications (PLC) also known as PLT or BPL.

IARU has already contributed to the ITU-R report SM2158 “ Impact of power line telecommunication systems on radiocommunication systems operating in the LF, MF, HF and VHF bands below 80 MHz“ where the acceptable criteria for degradation of the HF radio noise floor caused by PLT is defined as being 0.5dB. Work in WP1A will concentrate on the protection of radio services from the effects of PLT in range from 80 to 200MHz.

The IARU delegate to SG1 and its working parties is Peter Chadwick G3RZP: three input contributions have been prepared for this meeting. One of these is a report on the effects of intermodulation in power supplies causing the amateur band frequency notches in the PLT spectrum to be degraded: this report has been prepared from the work by Richard Marshall, G3SBA published in the RSGB RadCom magazine, and also points out the difficulty such effects could have on the PLT system itself.

A further input establishes the protection criteria for amateur stations operating in the 2 metre band: Ian White, GM3SEK contributed to this input, and it is considered that the amateur and amateur satellite services require protection such that PLT interference does not exceed -45dB m V/m in the main lobe of the antenna, with a separation between antenna and the PLT installation being at least 10 metres.

The third input is of a more general character showing that there are a number of non-amateur services that could suffer interference from PLT or its harmonics, such applications including social alarms for the elderly, pagers, medical implant telemetry, as well as broadcast, and when aggregation of radiation is concerned, aircraft navigation and communications. When the differences in range between PLT and mains leads and the social alarms and medical implant ‘base’ stations etc., are taken into account, the acceptable levels of radiation to protect the amateur services are of the same order as those needed to protect these other services.

In another posting to this club's excellent web site, VK3PC notes that "Access BPL" is for all purposes extinct in Australia. He says that it never really reached a critical mass in the market down there, and it is rapidly being abandoned for other systems.

Thankfully, a similar process seems to be at work in the USA, with the infamous Manassas system being the latest victim.

"Access BPL" differs from PLC aka PLT aka In-Home BPL in that it uses the power company's wires, which have been demonstrated to be excellent (if inadvertent) transmitting antennas. Less is known about the real-world, non-laboratory-conditions RF emission from PLC/ PLT/ In-Home BPL. This completely different system uses the house wiring to distribute high-bandwidth applications such as video on demand. Originally, wi-fi was not up to this task, though the technology is evolving rapidly.

While a bad situation has existed for some years in the UK, compounded by regulatory abdication, the problems there may or may not ever actually happen in the United States. US house wiring differs considerably from the 200-volt loops with fused plugs that are still fairly common in the UK.